Low-torque pivot bushing
A pivot has a low friction rotational property by allowing the elastomeric bushing to rotate with respect to the inner metal. A low friction material can be incorporated between these two components to facilitate the rotation, if desired. The elastomeric bushing helps to isolate the pivot joint and prevent the transmission of vibrations. In one embodiment, the elastomeric bushing is also allowed to pivot about an axis generally perpendicular to its axis of rotation.
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This application claims priority to provisional application 60/268,336 filed Feb. 12, 2001.
FIELD OF THE INVENTIONThe present invention relates to suspension pivot joints. More particularly, the present invention relates to an elastomeric bushing which allows articulation through flexing of the elastomeric material but also allows pivoting or rotation through sliding of the elastomeric material.
BACKGROUND OF THE INVENTIONAutomobiles and other vehicles normally incorporate suspension systems designed to absorb road shock and other vibrations. Many vehicles are provided with independent suspensions located at each wheel. These suspensions are designed to independently minimize the effect of shock loading on each of the wheels.
Suspension systems commonly employ stabilizer bars which interconnect independent suspensions on opposite wheels, lower control arms, upper control arms or strut assemblies, steering linkage and steering knuckles which are typically interconnected to each other through pivot joints such as ball joint assemblies.
Conventional ball joint assemblies comprise a ball stud seated in a socket. In a suspension link, each end of the link incorporates a socket, and a ball is seated in each socket. The stud, which extends from the ball of the ball joint assembly, is connected to one of the wheel assembly components. Ball joint assemblies allow articulation of the joined suspension components in both an angular and rotational direction through sliding of the joint components. The articulation due to sliding of the joint components offers low-torque rotation, but these designs do not offer shock isolation, since all of the components are typically made from rigid materials such as metal and/or hard plastic.
Another design for the pivot joints is an elastomeric bushing. The elastomeric bushing can be mechanically bonded, it can be chemically bonded during molding or it can be chemically bonded after molding. The elastomeric bushing allows articulation of the suspension components in both an angular and rotational direction through flexing of the elastomeric material. Elastomeric bushings offer excellent shock isolation but they have limited rotational capability because they rely on the flexing of the elastomeric material during rotation. The flexing of the elastomeric material adds a considerate amount of parasitic torque to the pivoting of the suspension and thus leads to a degraded ride performance. In addition, the parasitic torque can complicate the initial assembly of the suspension system.
The continued design for pivot joints includes the development of joint assemblies that offer the advantage of shock isolation but also provide the advantage of low-torque rotation.
SUMMARY OF THE INVENTIONThe present invention provides the art with a pivot joint which offers the isolation characteristics of an elastomeric bushing as well as the free rotation (low-torque) properties of a ball joint assembly. The pivot joint of the present invention provides for high articulation for improved ride and when used as a suspension pivot it provides for free rotation which enables convenient vehicle assembly. The present invention provides these advantages in an efficient package that can also include captivation, sealing and compression rate tunability.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limited the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
There is shown in
Referring now to
Referring now to
Referring now to
Sleeve 52 extends below a lower surface 60 of inner housing 50 and below a fully open end of outer housing 54 defined by an outward radial flange 62 of outer housing 54. Inner housing 50 defines a central bore 64, sleeve 52 defines a central aperture 66 and outer housing 54 defines an aperture 68 at a closed end of outer housing 54. Bore 64 and apertures 66 and 68 accommodate a bolt 70 which secures pivot joint 20 to the appropriate suspension component. The portion of sleeve 52 which extends beyond lower surface 60 will be compressed to provide a seal for pivot joint 20. After bolt 70 is tightened, a plastic cap 72 is fit within aperture 68 to also provide a seal for pivot joint 20. Outer housing 54 is secured to the appropriate suspension component by being press fit within an aperture or by other means known in the art. In the preferred embodiment, bolt 70 is secured to knuckle 12 or 36 or to the appropriate control rod and outer housing 54 is secured to control arm 18, 32 or 34.
Inner member 50 is coated with a low friction material 80 such as, but not limited to, PTFE. Sleeve 52 is bonded, by means known in the art, to outer housing 54. The components can be designed to be self-captivating through mechanical interlock, if desired. In addition, the components, as is shown in
During operation, pivot joint 20 offers shock isolation due to the elastomeric properties of sleeve 52. Sleeve 52 is also free to rotate about inner housing 50 with minimal windup and therefore low torque. The low-torque rotation is accomplished through the sliding of sleeve 52 on low friction material 80 located on inner member 50 while the outer surface of sleeve 52 is bonded to outer housing 54.
While
Referring now to
Elastomeric joint 114 comprises an inner tubular member 112, an annular elastomeric member 124 and a cylindrical outer member 126. Inner tubular member 122 extends through cylindrical outer member 126 with annular elastomeric member 14 being disposed between them. Typically, annular elastomeric member 124 is bonded to both inner tubular member 122 and cylindrical outer member 126. Cylindrical outer member 126 is press fit or otherwise secure within first bushing bore 116. A bolt (not shown) similar to bolt 70 described above, extend through inner tubular member 122 to secure sway bar link 110 to the vehicle and/or the vehicle's suspension system.
Referring now to
During operation, pivot joint 120 offers shock isolation due to the elastomeric properties of annular elastomeric member 134. Inner tubular member is free to rotate about annular elastomeric member 134 and outer generally cylindrical member 136 about a first axis 150 with minimal wind-up and therefore low torque. The low torque rotation is accomplished through the sliding of outer surface 140 on inner surface 142 with or without lubrication and/or low friction material 80 while the outer surface of annular member 134 is secured to outer member 136. In a similar manner, low torque pivoting is accomplished through the sliding of outer surface 140 on inner surface 142 with or without lubrication and/or low friction material 80 around a second axis 152 generally perpendicular to first axis 150. Circular extensions 144 of annular elastomeric member 134 cushion the interface between inner tubular member 132 and outer generally cylindrical member 136.
Pivot joint 120 can be a direct replacement for pivot joint 20 illustrated at various positions in
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
Claims
1. A pivot joint comprising:
- an inner member having an outer surface and an end surface generally perpendicular to said outer surface:
- an elastomeric member disposed around said inner member, said outer surface and said end surface of said inner member being rotatable within said elastomeric member;
- a cup-shaped outer member disposed around said elastomeric member, said cup-shaped outer member defining an outer wall, a closed end and a fully open end, said elastomeric member being fixedly secured to said outer member, said outer wall being disposed opposite to said outer surface of said inner member and said closed end being disposed opposite to said end surface of said inner member; and
- a low friction member disposed between said inner member and said elastomeric member, said low friction member being separate from said elastomeric member.
2. The pivot joint described in claim 1 wherein said inner member rotates within said elastomeric member around an axis.
3. The pivot joint described in claim 2 further comprising an axial retention member disposed between said inner member and said elastomeric member.
4. The pivot joint described in claim 3 wherein said axial retention member comprises a groove formed in one of said inner member and said elastomeric member and a rib formed on the other of said inner member and said elastomeric member, said rib being disposed within said groove.
5. The pivot joint described in claim 1 wherein said low friction member coats said inner member.
6. The pivot joint described in claim 1 wherein said elastomeric member is bonded to said outer member.
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Type: Grant
Filed: Feb 12, 2002
Date of Patent: Feb 15, 2005
Patent Publication Number: 20020111219
Assignee: The Pullman Company (Milan, OH)
Inventors: Edward M. Kraine, Jr. (Milan, OH), Joseph F. Cerri, III (Norwalk, OH), Kurt Stoll (Huron, OH)
Primary Examiner: Greg Binda
Attorney: Harness, Dickey & Pierce, PLC
Application Number: 10/074,944